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Tetsuya Morimoto, Hiroyuki Ohtsuka, Toshisuke Sakaki, and Masahiko Kawaguchi

✓ This 32-year-old man had undergone C3–7 laminectomy for posttraumatic cervical myelopathy associated with spinal canal stenosis. He developed recurrent myelopathy 5 years after the initial operation. Dynamic magnetic resonance (MR) imaging of the cervical spine demonstrated spinal cord compression with diffuse canal stenosis while the neck was in the extended position, whereas no significant stenosis was visualized in the neutral position. Sagittal and axial MR images of the affected levels demonstrated striking changes in the cervical spinal cord configuration. Because of an associated hard osteophyte formation and protruded disc, as well as a hypertrophied posterior longitudinal ligament, an anterior decompression and fusion with plate fixation were performed from C-4 to C-7. The postoperative course was uneventful, with subsequent neurological improvement. It is concluded that dynamic MR imaging aids the search for the cause of recurrent postlaminectomy cervical myelopathy after initial improvement following decompressive surgery.

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Keisuke Watanabe, Keiji Hashizume, Masahiko Kawaguchi, Aki Fujiwara, Noriyuki Sasaoka, and Hitoshi Furuya

Object

Recent evidence has indicated that the efficacy of the epidural blood patch (EBP) in the treatment of spontaneous CSF hypovolemia (SCH) is still limited. Therefore, further improvement of the EBP technique is an important clinical challenge. The authors describe a series of cases of SCH treated with fluoroscopically guided placement of an EBP and followed up with subsequent spinal CT scans.

Methods

Thirteen patients with SCH that was proven on CT myelography studies underwent epidural puncture under fluoroscopic guidance and received an injection of a mixture of contrast medium and autologous blood. Contrast medium was injected to cover the area of CSF leakage during EBP guided by fluoroscopy, and the spread of the blood was subsequently evaluated using spinal CT scanning. If the amount of blood injected was insufficient to cover the leakage area, a second EBP was performed at a later date.

Results

At the first EBP procedure, a mixture with a mean volume of 9.4 ml (range 3–20 ml) was injected, and subsequent spinal CT scans revealed contrast enhancement in the desired epidural space in 12 of 13 patients. In 2 patients, a second EBP was required because of insufficient coverage of the leakage area or delayed recurrence of headache. In all patients, a complete recovery from orthostatic headache was obtained after the last EBP.

Conclusions

The results indicated that fluoroscopically guided EBP and subsequent spinal CT scans may provide a highly effective therapy in patients with SCH proven on CT myelography studies.

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Tsunenori Takatani, Yasushi Motoyama, Young-Soo Park, Taekyun Kim, Hironobu Hayashi, Ichiro Nakagawa, Masahiko Kawaguchi, and Hiroyuki Nakase

OBJECTIVE

Reportedly, tetanic stimulation prior to transcranial electrical stimulation (TES) facilitates elicitation of motor evoked potentials (MEPs) by a mechanism involving increased corticomotoneuronal excitability in response to somatosensory input. However, the posttetanic MEP following stimulation of a pure sensory nerve has never been reported. Furthermore, no previous reports have described posttetanic MEPs in pediatric patients. The aim of this study was to investigate the efficacy of posttetanic MEPs in pediatric neurosurgery patients and to compare the effects on posttetanic MEP after tetanic stimulation of the sensory branch of the pudendal nerve versus the standard median and tibial nerves, which contain a mixture of sensory and motor fibers.

METHODS

In 31 consecutive pediatric patients with a mean age of 6.0 ± 5.1 years who underwent lumbosacral surgery, MEPs were elicited by TES without tetanic stimulation (conventional MEPs [c-MEPs]) and following tetanic stimulation of the unilateral median and tibial nerves (mt-MEPs) and the sensory branch of the pudendal nerve (p-MEP). Compound muscle action potentials were elicited from abductor pollicis brevis (APB), gastrocnemius (Gc), tibialis anterior (TA), and adductor hallucis (AH) muscles. The success rate of monitoring each MEP and the increases in the ratios of mt-MEP and p-MEP to c-MEP were investigated.

RESULTS

The success rate of monitoring p-MEPs was higher than those of mt-MEPs and c-MEPs (87.5%, 72.6%, and 63.3%, respectively; p < 0.01, adjusted by Bonferroni correction). The mean increase in the ratio of p-MEP to c-MEP for all muscles was significantly higher than that of mt-MEP to c-MEP (3.64 ± 4.03 vs 1.98 ± 2.23, p < 0.01). Subanalysis of individual muscles demonstrated significant differences in the increases in the ratios between p-MEP and mt-MEP in the APB bilaterally, as well as ipsilateral Gc, contralateral TA, and bilateral AH muscles.

CONCLUSIONS

Tetanic stimulation prior to TES can augment the amplitude of MEPs during pediatric neurosurgery, the effect being larger with pudendal nerve stimulation than tetanic stimulation of the unilateral median and tibial nerves. TES elicitation of p-MEPs might be useful in pediatric patients in whom it is difficult to elicit c-MEPs.

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Ryuta Matsuoka, Yasuhiro Takeshima, Hironobu Hayashi, Tsunenori Takatani, Fumihiko Nishimura, Ichiro Nakagawa, Yasushi Motoyama, Young-Su Park, Masahiko Kawaguchi, and Hiroyuki Nakase

OBJECTIVE

False-positive intraoperative muscle motor evoked potential (mMEP) monitoring results due to systemic effects of anesthetics and physiological changes continue to be a challenging issue. Although control MEPs recorded from the unaffected side are useful for identifying a true-positive signal, there are no muscles on the upper or lower extremities to induce control MEPs in cervical spine surgery. Therefore, this study was conducted to clarify if additional MEPs derived from facial muscles can feasibly serve as controls to reduce false-positive mMEP monitoring results in cervical spine surgery.

METHODS

Patients who underwent cervical spine surgery at the authors’ institution who did not experience postoperative neurological deterioration were retrospectively studied. mMEPs were induced with transcranial supramaximal stimulation. Facial MEPs (fMEPs) were subsequently induced with suprathreshold stimulation. The mMEP and subsequently recorded fMEP waveforms were paired during each moment during surgery. The initial pair was regarded as the baseline. A significant decline in mMEP and fMEP amplitude was defined as > 80% and > 50% decline compared with baseline, respectively. All mMEP alarms were considered false positives. Based on 2 different alarm criteria, either mMEP alone or both mMEP and fMEP, rates of false-positive mMEP monitoring results were calculated.

RESULTS

Twenty-three patients were included in this study, corresponding to 102 pairs of mMEPs and fMEPs. This included 23 initial and 79 subsequent pairs. Based on the alarm criterion of mMEP alone, 17 false-positive results (21.5%) were observed. Based on the alarm criterion of both mMEP and fMEP, 5 false-positive results (6.3%) were observed, which was significantly different compared to mMEP alone (difference 15.2%; 95% CI 7.2%–23.1%; p < 0.01).

CONCLUSIONS

fMEPs might be used as controls to reduce false-positive mMEP monitoring results in cervical spine surgery.

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Yoshiharu Kawaguchi, Takeshi Oya, Yumiko Abe, Masahiko Kanamori, Hirokazu Ishihara, Taketoshi Yasuda, Shigeharu Nogami, Takeshi Hori, and Tomoatsu Kimura

Object. Spinal stenosis due to lumbar ossified lesions is a rare pathological entity. The authors retrospectively evaluated the clinical features and surgical results associated with cases involving lumbar ossified lesion—induced stenosis.

Methods. Data obtained in 20 surgically treated patients with lumbar hyperostotic spinal stenosis were included. To evaluate the background of the disease, body mass index and general complications were assessed. Whole-spine radiological examination was conducted. The presence of ossification of the posterior longitudinal ligament or ossification of the ligamentum flavum was evaluated. Surgical results were classified according to the Japanese Orthopaedic Association (JOA) scale. In the patients in whom neurological deterioration was observed during follow up, the causes of deterioration were reviewed. Seven patients (35%) were obese and six patients (30%) suffered diabetes mellitus. Twelve patients harbored coexisting cervical and/or thoracic ossified lesions. The overall mean JOA score improved from 10.2 to a peak of 22.5; at last follow-up examination the mean JOA score was 20.9. In female and older patients with a long history of preoperative symptoms, a low preoperative JOA score, and other spinal lesions, recovery tended to be poorer. Recovery was poor in one patient, and neurological deterioration due to coexisting ossified spinal lesions occurred in another patient during the follow-up period.

Conclusions. Because coexisting ossified lesions were frequently seen, whole-spine analysis is recommended. Early diagnosis and appropriate treatment are important to achieve a better surgical outcome.